Fleet admiral was a militaryrank, the equivalent of which was used by the service organizations of many civilizations. As a traditional grade, fleet admiral was the most senior flag officer rank of a naval organization, above all the flag admiral grades save for commander-in-chief. In comparison to army ranking systems, this rank was equivalent to the most senior general rank, such as Field Marshal or General of the Army.

In these situations when an officer referred to an admiral as "fleet admiral" they could simply have been calling them fleet admiral because they were acting as the head of a fleet. Field promotion is another possibility.

Currently, in the United States Navy, the rank of fleet admiral (FADM) is inactive and has not been awarded since World War II. It is the equivalent of the United States Army's rank of general of the army (GA) with both ranks' insignia appearing as five stars arranged in a pentagonal shape.

There has never been a rank shown in a live action production senior to the Starfleet position of fleet admiral; however, there have been at least two senior ranks mentioned in non-canonical comic books and reference materials.

A senior rank of grand admiral has also appeared in Star Trek comic books, making its first mention in "The Wormhole Connection". The rank of grand admiral is said to have existed in 2285 and has a special uniform with shoulder boards worn on the red maroon jacket uniform. The rank also appeared in the novel The Sorrows of Empire, held first by the counterpart Garth of Izar, then by the counterpart Matt Decker and then by Spock, before he becomes Emperor of the Terran Empire. However, grand admiral is far better known in the Star Wars franchise, where it is held by the character of Grand Admiral Thrawn.